Heat treatment furnace and conveyor therefor



June 16, 1964 E. w. JOHNSON ETAL 3,137,485

HEAT TREATMENT FURNACE AND CONVEYOR THEREFOR Filed April 17, 1961 2 Sheets-Sheet 1 swan/wrote j dzazbz 28 7 Clo/1725072 far-Z Fay/5072 a & V awn 7 June 16, 1964 E. w. JOHNSON ETAL 3,137,485

HEAT TREATMENT FURNACE AND CONVEYOR THEREFOR 2 Sheets-Sheet 2 Filed April 17, 1961 United States Patent f 3,137,485 HEAT TREATMENT FURNACE AND CONVEYOR THEREFOR Edwin W. Johnson, Cranston, and Carl Paulson, Provideuce, R.I., assignors to C. I. Hayes, Inc., Cranston,

11.1., a corporation of Rhode Island Filed Apr. 17, 1961, Ser. No. 103,364 2 Claims. (Cl. 263-6) The present invention relates generally to heat treatment furnaces and is more particularly concerned with the provision of novel and improved conveyor means for automatically moving a series of spaced work loads through said furnace.

While it is a simple matter to have an automatic or motor driven conveyor for propelling a series of spaced work loads through a furnace or the like, a problem arises Where an elevated heat treatment chamber is provided in the furnace, thereby necessitating the presence of an elevator for receiving the work loads and lifting them into the heating chamber for treatment. Obviously, the presence of such an elevator centrally positioned within a furname makes it impossible to use a continuous conveyor for automatically carrying the work loads through the furnace since the conveyor would interfere with the raising and lowering of the elevator. Thus, it is a primary object of the instant invention to provide specially designed conveyor means for automatically controlling movement of a work load from the loading end of a furnace, through a preheating area, onto an elevator on which the work load may be raised and lowered, then through a cooling area, and finally to the unloading station in the furnace.

Another object of our invention is the provision of a conveyor system which when utilized in connection with an elevator heat treatment furnace enables a controlled atmosphere to be utilized therein without any appreciable danger of contamination.

Another object of our invention is the provision of a conveyor system effective for automatically moving parts or containers through an enclosed treatment area, without the necessity of entering the enclosed area other than for loading and unloading purposes.

Still another object of our invention is the provision of novel and improved conveyor means for a furnace of the type described having means for moving said conveyor through an operating cycle starting with a neutral position wherein the furnace elevator is free to move up and down, then to a reverse position wherein the work loads in the furnace are engaged for movement, then to a forward position, at which time the work loads are moved forwardly one step, and then back to the aforesaid neutral position.

Still another object is the provision of conveyor means of the character described which is effective and economical in operation, is of rugged and durable construction, and is capable offunctioning at relatively high heat treatment temperatures.

Other objects, features and advantages of the invention will become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.

In the drawings which illustrate the best mode presently contemplated by us for carrying out our invention:

FIG. 1 is a front elevational view, partly in section, of a furnace embodying our invention;

FIG. 2 is a diagrammatic view showing the means for controlling an operational cycle of our invention;

FIG, 3 is a section, on an enlarged scale, taken on line 33 of FIG. 1;

FIG. 4 is a fragmentary perspective view, on an enlarged scale, illustrating the hearth construction which forms a part of our invention;

3,137,485 Patented June 16, 1964 FIG. 5 is a fragmentary perspective view, on an enlarged scale, of one of the rams which form a part of our invention; and

FIG. 6 is a front elevational view, partly in section, of the ram shown in FIG. 5.

In Patent No. 2,891,659 there is shown a conveyor system for a heat treatment furnace wherein the work loads are conveyed automatically through the furnace in a predetermined spaced relation. The system of said patent involves the use of retractable latches, and in that respect is somewhat similar to the instant invention, as will hereinafter become apparent. However, in the construction of Patent No. 2,891,659 the heat treatment chamber is at the same level as the conveyor, i.e., the conveyor itself passes through the heat treatment chamber. It has been found that in certain situations it is not desirable to have the conveyor means pass through the heat treatment chamber, since the relatively high temperatures may cause weakening or distortion of the conveyor structure. Accordingly, it is not uncommon for heat treatment furnaces of this general type to have an elevated heat treatment chamber, an elevator being provided for receiving the work load and lifting it into said heat treatment chamber, and then lowering the work load from said chamber when the heat treatment has been completed. It is obvious that in such a furnace the continuous conveyor of Westeren Patent No. 2,891,659 could not be used, since the presence of an elevator in alignment with the heat treatment chamber would interfere with the operation of such a continuous conveyor. The instant invention overcomes this problem and provides a conveyor system wherein the work loads are fed through the furnace automatically in spaced intervals and are automatically positioned upon the heat treatment elevator, the elevator then being free to raise and lower, said conveyor means then removing the work load from the elevator platform and carrying it to the unloading end of the furnace. I

Referring now to the drawings, there is shown generally at 10 a heat treatment furnace comprising a loading area 12, a preheating area 14, an elevated heat treatment chamber 16, a cooling area 18, and an unloading station 20. The loading area 12 comprises a loading opening 22 normally covered by a pivotal flap 24, it being noted that said opening is at a'considerably lower level than the level on which the work loads 26 pass through the furnace. This arrangement reduces to a minimum the possibility of contamination of the controlled treatment atmosphere within the furnace 10 by seepage therein of the surrounding air during the loading operation, it being understood that in the heat treatment of stainless steel and the like, with which the instant invention is concerned, the treatment is carried out in a carefully controlled atmosphere, such as a hydrogen atmosphere, for example, and it is important that contamination of said treatment atmosphere, such as by introduction of air, be kept at a. rmmmum.

A loading elevator 28 is provided in the loading area 12, said elevator being movable to the lowered position shown in dotted lines in FIG. 1 to receive a work load introduced through opening 22. The elevator may then be raised by any suitable and conventional means to the full-line position of FIG. 1, wherein the upper surface of said elevator is in alignment with hearth sections 30 and 32, located in the preheating and cooling areas of the furnace, respectively. The unloading station 20 of furnace 10 is similar in construction to the loading area just described, it being noted that an unloading or exit opening 34 is provided, normally covered by pivotal flap 36. An unloading'elevator 38 is provided for receiving a work load from hearth section 32 and then lowering said work load to the dotted-line position shown in FIG. 1, wherein said work load may beremoved from the furnace through exit opening 34. Located between hearth sections 30 and 32 is a third elevator 40, it being noted that said elevator, when in its lowered position as shown in full lines in FIG. 1 is in alignment with said hearth sections, and when in its raised position as per the dotted line illustration in FIG. 1, is located within heating chamber 16.

In accordance with our invention, means are provided for automatically conveying each work load through the furnace from elevator 28 to elevator 40 and then to elevator 38, while at the same time leaving elevator 4%) unimpeded for raising a work load into the heating chamher. As will be seen most clearly in FIGS. 3 and 4, the hearth sections 30 and 32 each comprise a substantially flat surface having a centrally disposed, longitudinally extending slot 42 which communicates with a channel 44, said channel in turn communicating with a depending channel 46, said channel 46 being of lesser width than channel 44, as defined by inwardly extending shoulders 48. It is important to note that elevators 28, 38 and 4% each have a channel 50 extending thereacross, said channels being in alignment with the aforesaid channels 44 and having substantially the same configuration. Although as hereinbefore pointed out hearth section 30 has the same slot and channel structure as hearth section 32, it will be seen from FIG. 1 that the depending channel 46 which is associated with hearth section 319 is of greater depth than the depending channel associated with hearth section 32, and the former is indicated in the drawings at 46a.

Slidably positioned in the upper channel 44 associated with hearth section 3% in an elongated ram 52, it being noted that said ram is of substantially the same length as said hearth section, or, expressed differently, said ram is slightly shorter than the distance between elevators 28 and 40. A similar ram 54 is slidably positioned in the channel 44 associated with hearth section 32, it once again being noted that said ram is of substantially the same length as its hearth section and is of just slightly lesser length than the distance between elevators 40 and 38. Except for the fact that they are of different lengths, the rams 52 and 54 are of substantially identical construction and are shown in detail in FIGS. and 6. Thus, ram 52 comprises a bottom plate 56, side walls 58, and a center portion 6b which terminates short of the opposite ends of the ram to provide recesses 62, in which are pivotally mounted a retractable latch 64. As will be seen most clearly in FIG. 6, latch 64 is pivotally mounted on pin 66, and the distribution of weight in the latch is such that it is normally in its upwardly disposed position, as illustrated in full lines in FIG. 6. It will be seen, however, that upon movement of the ram 52 to the left, when viewing FIGS. 1, 5 or 6, the latch is free to pivot to a retracted position as illustrated in dotted lines in FIG. 6. As will be seen in FIG. 1, ram 52 is provided with a latch 64 at each of its ends, while ram 54 is provided with a similar latch at each of its ends, and also a third one positioned substantially centrally of the ram. Each of the rams 52 and 54 is provided with a pair of depending lugs 68, the purpose of which will soon become apparent.

The work loads 26 each comprise a container which may take any suitable form, such as a rectangular basket, for example, said container having a plurality of longitudinally extending runners 70 secured to the outside of its bottom wall, as shown most clearly in FIG. 3. In addition, each basket at its forward lower edge is provided with a cross bar 72, the lower edge of said bar being spaced slightly above the lowermost edges of runners 70. It is important to note that upon movement of rams 52 and 54 to the left when viewing FIG. 1, the latches 64 will be cammed to their retracted position and will pass freely beneath bars 72. As soon as the latches have passed by the bar 72, however, they will automatically move by gravity to their operative, or full-line position as viewed in FIG. 6, whereupon when the rams move back to the right, the latches will engage the bars 72 to move the work loads 26 toward the unloading end of the furnace. The means for effecting and controlling the reciprocal movement of rams 52 and 54 will now be described.

Located beneath each of the rams 52 and 54 is a continuous conveyor chain 74 and 76, respectively. More specifically, conveyor chain 74 is located within channel 46a and extends around a drive roller 78 mounted on drive shaft 89 and three idler rollers 82. The chain 74 is connected to ram 52 at lugs 68. By the same token, conveyor chain 75, which is located within channel 46, extends around drive roller 84 mounted on shaft 86 and idler roller 88. Chain 76 is also connected to ram 54 by its lugs 68 and in this connection is shown most clearly in FIG. 3, it being noted that the chain is connected to the lugs by means of a cross pin 90. This is the same structure that is utilized for connecting chain 74 to ram 52. It will be noted that hearth section 32 is located within a water jacket 92 since this represents the cooling area of the furnace.

Located exteriorly of the furnace 10 and within any suitable enclosure (not shown) associated with said furnace is the means for driving and controlling movement of conveyors 74 and 76. As will be seen in FIG. 2, a motor 94 drives shaft by a suitable pulley 96, it being understood that shaft 81) extends into furnace 10 through a suitable stuffing box 98. As has been hereinbefore described, drive wheel 78 is mounted on shaft 80, and hence it will be seen that motor 94 controls movement of conveyor 74. Rotation of shaft 86 is synchronized with rotation of shaft 80 by means of an endless belt whereupon it will be seen that conveyors 74 and 76 always move in unison. This means for controlling reciprocal movement of conveyors 74 and 76 comprises an endless belt 102 which carries an actuating finger 104. A pair of double-pole, double-throw switches 106 and 198 are provided and are adapted to be engaged by finger 104 to define the limits of travel of conveyors 74 and 76. A third double-pole, double-throw switch 110 is located intermediate the first two switches and is adapted to be actuated by a trigger member 112 which is pivotally mounted at 114. The trigger member 112 has a forward portion 116 which is adapted to engage switch 118, as will be hereinafter described in mo're detail, and said trigger member further comprises a cam portion 118 which is adapted to be engaged by actuating finger 104. The trigger 112 further has a rearwardly extending portion 120 which cooperates with springs 122 to resiliently hold the trigger in a position wherein cam portion 118 will be engaged by finger 104 when the belt 102 is moving.

As seen in FIGS. 1 and 2, the apparatus is in what may be called its neutral position. In this neutral position, it will be seen that rams, 52 and 54 are positioned so that all of the elevators, and particularly elevator 40, are free for movement without any interference from said rams. Thus it will be seen that the apparatus is always in this neutral position when elevator 40 is raised to position a work load within heating chamber 16. After the heat treatment of a given work load has been completed, elevator 40 is lowered to the full-line position shown in FIG. 1 and the apparatus is ready to undergo its cycle of operation whereupon all of the work loads will automatically move up one step, whereupon the next succeeding work load will be positioned on elevator 40, ready to be raised into the heating chamber. In order to effect this cycle of operation, a suitable starting switch (not shown) is actuated to energize motor 94 and start driving conveyors 74 and 76, as well as belt 102, in a counterclockwise direction. This initial energization causes actuating finger 104 to ride over cam 118, whereupon springs 122 automatically position trigger 112 so that it is not actuating switch 110. Belt 102 will continue to move in the rams.

the direction of the arrow shown in FIG. 2, or in a counterclockwise direction, until actuating finger 104 reaches switch 108. Upon engagement of switch 108 by finger 104, motor 94 is reversed whereupon belt 102, and conveyors 74 and 76, commence to move in a clockwise direction. The movement of belt 102, and conveyors 74 and 76, from the neutral position to engagement with switch 108 may be considered the reverse stroke of our mechanism, since during this movement, rams 52 and 54 are being retracted, or moved to the left when viewing FIG. 1, a sufficient distance for latches 64 to pass behind cross bars 72 of the next rearwardly adjacent work loads 26. As hereinbefore explained, the latches 64 will automatically depress as they pass beneath the cross bar 72, but once behind the cross bar 72, the latches will automatically move upwardly to their operative position. As soon as motor 94 has been reversed by actuation of switch 108, and belt 102 starts moving in a clockwise direction, it will be seen that conveyors 74, 76 also move in a clockwise direction carrying therewith rams 52 and 54 on their forward stroke, or to the right, as viewed in FIG. 1. Due to the engagement of the latches 64 with the work loads 26, said work loads will be carried forwardly with As belt 102 moves in a clockwise direction, it will be seen that finger 104 will engage cam 118, but this will have no effect on switch 110 since this engagement actually forces trigger 112 away from switch 110, and hence belt 102 will continue its clockwise movement until finger 104 reaches switch 106. Actuation of switch 106 once again causes motor 94 to reverse, whereupon belt 102 once again commences to move in a counterclockwise direction. During this movement, the rams are being retracted from the forwardmost point of their stroke back to their neutral position, which is reached as soon as finger 104 strikes cam 118 to pivot trigger 112 in a clockwise direction so as to actuate switch 110. This automatically deenergizes motor 94 and completes the cycle of operation.

Thus, it will be seen that with the apparatus in the position shown in FIG. 1, the first step in the operation of our invention wouldbe to lower unloading elevator 38, unload the work load 26 located thereon through the unloading opening 34, and then once again raise the elevator 38 to its upper position. Assuming that the work load located on elevator 40 has already been heat treated, the cycle of operation is then initiated, whereupon each work load will move up one step. More specifically, ram 52 will automatically retract to engage the work load located on elevator 28 and the work load which is in the preheating area 14. At the same time, ram 54 will retract to engage the work load which is located on elevator 40, and the two work loads which are in the cooling area. During the forward stroke of the rams, each of the work loads will be moved up one notch, whereupon when neutral position of the parts has been reached, and the cycle of operation automatically terminated as hereinbefore described, elevator 28 will be lowered to receive a new work load, while elevator 40 will be raised into the heating chamber to treat the work load which is positioned thereon. At the same time, unloading elevator 38 may be lowered to remove the work load thereon from the furnace.

Thus it will be seen that there has been provided in accordance with our invention an arrangement wherein movement of the work loads through an elevator-type heat treatment furnace of the character described is completely automatic, except for the loading and unloading steps. This reduces the likelihood of contamination of the treatment atmosphere within the furnace to a minimum, and at the same time provides a highly expeditious production operation. While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described exoept insofar as indicated by the scope of the appended claims. For example, even though not disclosed, it will be understood that suitable interlocks or safety switches may be provided for insuring that elevator 40 can raise and lower only when the apparatus is in its neutral position.

What is claimed is:

1. A furnace comprising an elongated horizontally disposed housing having an entrance end and an exit end, a pair of spaced aligned hearth sections extending horizontally and longitudinally through said furnace, a heat treatment chamber in said furnace vertically disposed from but in alignment with the space between said hearth sections, an elevator in said furnace located between said hearth sections, means for moving said elevator vertically between a first position wherein it is horizontally aligned with said hearth sections and a second position wherein it is within said heat treatment chamber, reciprocal pusher means for automatically moving a work load from the hearth section adjacent said entrance end onto said elevator and then on to the other hearth section, said pusher means comprising a pair of spaced rams located adjacent said hearth sections and spaced from each other by a distance at least as great as the width of said elevator, means for reciprocating said rams in unison whereby the spaced relation between the rams always remains constant, said rams each having a retractable latch movable between an operative position and a retracted position, means normally biasing said latches to their said operative position whereupon as said rams move toward the said exit end work loads positioned on said hearth sections are engaged and moved therewith, said latches being depressible to retracted position when said rams move back toward said entrance end whereby said latches pass freely by the work loads, and means for automatically cycling said pusher means from a neutral position wherein said elevator is unobstructed for vertical movement and wherein said rams are located with their latches slightly in advance of the work loads, to a rearward position wherein said rams move back a sufiicient distance for their latches to pass behind adjacent work loads including any work load located on said elevator, and then to a forward position wherein said rams and latches simultaneously move a. work load from the hearth section adjacent the said entrance end onto said elevator, a work load from said elevator onto the other hearth section, and a work load on the other hearth section toward said exit end.

2. The furnace of claim 1 further characterized in that said elevator and hearth sections all have aligned, longitudinally extending channels in communication with their upper surfaces, said rams being movable through said channels, and said latches extending upwardly from said rams to a point above the said upper surfaces.

References Cited in the file of this patent UNITED STATES PATENTS 2,891,659 Westeren June 23, 1959 2,898,101 Hannum et al Aug. 4, 1959 2,978,237 Frank Apr. 4, 1961 

1. A FURNACE COMPRISING AN ELONGATED HORIZONTALLY DISPOSED HOUSING HAVING AN ENTRANCE END AND AN EXIT END, A PAIR OF SPACED ALIGNED HEARTH SECTIONS EXTENDING HORIZONTALLY AND LONGITUDINALLY THROUGH SAID FURNACE, A HEAT TREATMENT CHAMBER IN SAID FURNACE VERTICALLY DISPOSED FROM BUT IN ALIGNMENT WITH THE SPACE BETWEEN SAID HEARTH SECTION, AN ELEVATOR IN SAID FURNACE LOCATED BETWEEN SAID HEARTH SECTIONS, MEANS FOR MOVING SAID ELEVATOR VERTICALLY BETWEEN A FIRST POSITION WHEREIN IT IS HORIZONTALLY ALIGNED WITH SAID HEARTH SECTION AND A SECOND POSITION WHEREIN IT IS WITHIN SAID HEAT TREATMENT CHAMBER, RECIPROCAL PUSHER MEANS FOR AUTOMATICALLY MOVING A WORK LOAD FROM THE HEARTH SECTION ADJACENT SAID ENTRANCE END ONTO SAID ELEVATOR AND THEN ON TO THE OTHER HEARTH SECTION, SAID PUSHER MEANS COMPRISING A PAIR OF SPACED RAMS LOCATED ADJACENT SAID HEARTH SECTIONS AND SPACED FROM EACH OTHER BY A DISTANCE AT LEAST AS GREAT AS THE WIDTH OF SAID ELEVATOR, MEANS FOR RECIPROCATING SAID RAMS IN UNISON WHEREBY THE SPACED RELATION BETWEEN THE RAMS ALWAYS REMAIN CONSTANT, SAID RAMS EACH HAVING A RETRACTABLE LATCH MOVABLE BETWEEN AN OPERATIVE POSITION AND A RETRACTED POSITION, MEANS NORMALLY BIASING SAID LATCHES TO THEIR SAID OPERATIVE POSITION WHEREUPON AS SAID RAMS MOVE TOWARD THE SAID EXIT END WORK LOADS POSITIONED ON SAID HEARTH SECTIONS ARE ENGAGED AND MOVED THEREWITH, SAID LATCHES BEING DEPRESSIBLE TO RETRACTED POSITION WHEN SAID RAMS MOVE BACK TOWARD SAID ENTRANCE END WHEREBY SAID LATCHES PASS FREELY BY THE WORK LOADS, AND MEANS FOR AUTOMATICALLY CYCLING SAID PUSHER MEANS FROM A NEUTRAL POSITION WHEREIN SAID ELEVATOR IS UNOBSTRUCTED FOR VERTICAL MOVEMENT AND WHEREIN SAID RAMS ARE LOCATED WITH THEIR LATCHES SLIGHTLY IN ADVANCE OF THE WORK LOADS, TO A REARWARD POSITION WHEREIN SAID RAMS MOVE BACK A SUFFICIENT DISTANCE FOR THEIR LATCHES TO PASS BEHIND ADJACENT WORK LOADS INCLUDING ANY WORK LOAD LOCATED ON SAID ELEVATOR, AND THEN TO A FORWARD POSITION WHEREIN SAID RAMS AND LATCHES SIMULTANEOUSLY MOVE A WORK LOAD FROM THE HEARTH SECTION ADJACENT THE SAID ENTRANCE END ONTO SAID ELEVATOR, A WORK LOAD FROM SAID ELEVATOR ONTO THE OTHER HEARTH SECTION, AND A WORK LOAD ON THE OTHER HEARTH SECTION TOWARD SAID EXIT END. 